My uneducated concern is that masks that are not intended to seal may not allow air to flow sufficiently easily through their “filter” part (without it turning out to be a problem during “normal” use due the air easily flowing through the edges). Re volume argument, maybe we also need to consider the volume of the air we inhale each time (and whether that volume becomes smaller if something is partially blocking the air flow, and whether we notice).
My uneducated concern is that masks that are not intended to seal may not allow air to flow sufficiently easily through their “filter” part (without it turning out to be a problem during “normal” use due the air easily flowing through the edges). Re volume argument, maybe we also need to consider the volume of the air we inhale each time (and whether that volume becomes smaller if something is partially blocking the air flow, and whether we notice).